Among both athletes and non-athletes, the popularity of weight training exercise has substantially increased in the past ten years. In addition to the use of traditional "free weights," i.e., plate-loaded barbells or dumbbells, weight training exercises are also performed with a number of specialized exercise machines that work a particular muscle group through a prescribed motion or exercise maneuver. Generally, for most exercise maneuvers that may be performed either on a machine or with free weights, exercise machines tend to be safer. Moreover, from a practical standpoint, certain exercise maneuvers are simply more efficient and beneficial when performed on an exercise machine, particularly when the major purpose for performing weight training is to rehabilitate an injured limb.
In addition to rehabilitation, another purpose of weight training is the prevention of injuries. By building up the muscles associated with a particular movement and the joints involved with that movement, the likelihood of injury can be reduced.
The deltoid muscles on the tops of the shoulders are exercised during a movement referred to as lateral shoulder abduction. An exerciser may exercise the deltoid muscles by grasping dumbbells in each hand and laterally raising them upwardly through a lateral shoulder abduction movement, with the arms bent or extended at the elbows. However, it is difficult to perform this exercise with dumbbells in a steady, controlled manner. Rather, the movement is somewhat jerky, and if the exerciser is using too much weight, this manner of performing this exercise may cause injury. Optimally, to maximize muscular benefit to the deltoid muscles, steady lateral abductive movement through a relatively large range of motion is desirable. The above-described dumbbell exercise does not provide either steady movement or movement through an extended range of motion.
One known lateral raise exercise machine addresses some of the disadvantages associated with the use of dumbbells to exercise the deltoid muscles through a lateral shoulder abduction. This method locates the exerciser in a seated position, with graspable handles located on opposite sides of the seat. The handles are connected to arms which extend forwardly from rotatable eccentric cams located behind the seat. The cams rotate in a vertical plane that is perpendicular to the forward facing direction of the seat. Each cam is connected to a chain, with one end of each chain adapted to ride around the respective cam and an opposite end of each chain connected to a selectable number of stacked weight plates.
By engaging the outer portions of the forearms against inwardly directed surfaces of pads mounted on the insides of the extenders, and then grasping the handles located forwardly of these pads, an exerciser supported on the seat laterally raises the arms in a lateral shoulder abduction to exercise the deltoid muscles. With this machine, the exerciser is able to work the deltoid muscles in a smooth manner through a relatively large range of lateral shoulder abductive motion.
Nevertheless, this exercise machine suffers from a number of disadvantages. First, from a practical standpoint, the rotatable cams and chains require maintenance, as outlined in applicant's copending patent application Ser. Nos. 514,869 and 514,839. Otherwise, undesired friction builds up and adds to the weight resistance that must be moved by the exerciser during the exercise. Second, the machine itself is relatively expensive. For some exercise facilities, the benefits of this machine may not justify its costs. Third, although this exercise machine does allow separate exercise of the deltoid muscle on either side of the body, this manner of single side exercise is inconvenient because it requires disconnection of one of the cams from the weight stack and a change to a lesser weight. Fourth, this lateral raise exercise machine does not seem to quite "fit" the actual musculoskeletal make-up of a human being when performing a lateral shoulder abduction movement. For many exercisers, the plane of lateral movement causes some impingement of the shoulder joint, and as a result, use of this exercise machine may feel awkward or uncomfortable.
It is an object of this invention to provide an improved lateral raise exercise machine.
It is another object of this invention to provide the lateral raise exercise machine which, compared to a prior lateral raise exercise machine, is relatively inexpensive and more naturally accommodates the musculoskeletal make-up of a human being.
It is still another object of the invention to provide a lateral raise exercise machine that is equally suitable for convenient simultaneous exercise of both deltoid muscles or alternate exercise of one deltoid muscle at a time.